what does dead hair algae look like?

That's how it appears, if I remember correctly after it's been bleached. Did you bleach it? It should come off by itself, but you can probably pull it off easily at this point.
Len
 
Just because its white doesn't mean it's dead. I've had my share of algae, and this was one of them. It actually grows white, as long strings, sparsely branched. Don't assume that it died off, because it will keep growing. Mine even grows on my snails. I don't have a way to get rid of it, but my tank seems to be past it. In fast, I lost MOST algae when I started fertilizing more - N, P, K and traces. If you're not fertilizing, you should look into it. If you are, you may want to increase some levels, depending on what you're dosing already.
 
If it's the real coarse algae and almost impossible to pull off the plant it's probably Black Beard/Brush Algae.
If you don't have much of it, just try cutting out the affected areas. If you have a lot, the only thing I know of that's affective it a bleach treatment. Black outs don't work with BBA.
Len
 
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